EPA-AA-TSS-83-5
Technical Report
Determination of a Range of Concern
for Mobile Source Emissions
of Formaldehyde
Based Only on its Toxicological Properties
by
Penny M. Carey
July 1983
NOTICE
Technical reports do not necessarily represent final EPA
decisions or positions. They are intended to present
technical analysis of issues using data which are currently
available. The purpose in the release of such reports is to
facilitate the exchange of technical information and to
inform the public of technical developments which may form
the basis for a final EPA decision, position or regulatory
action.
U. S. Environmental Protection Agency
Office of Air, Noise and Radiation
Office of Mobile Sources
Emission Control Technology Division
Technical Support Staff
2565 Plymouth Road
Ann Arbor, Michigan 48105
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Summary
This paper describes an effort by the Emission Control
Technology Division of the EPA to suggest a range of concern
for formaldehyde (HCHO) emissions from mobile sources. As
defined in this report, the lower value of the range will be
the lowest level at which there is some suggestion of adverse
physiological effects. The upper level of the range of
concern is that pollutant concentration above which the
studies show that the pollutant causes so great a health
hazard as to strongly suggest it be avoided. The region
between these limits will be termed the "ambient air range of
concern", indicating the range of adverse physiological
effects caused by exposure to various concentrations of the
pollutant. This range is also expressed in terms of a
vehicle emission range of concern to show what levels of
vehicle emissions would create ambient concentrations within
the ambient air range of concern.
In light of the action called for in section 202(a)(4) of the
Clean Air Act (CAA) (1)* and due to a concern within industry
as to what emission levels will be used as the basis for the
*Numbers in parentheses denote references listed at end of
report.
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evaluation of current and future lechnologies, a methodology
was developed prior to this paper for bracketing a range of
concern for various unregulated pollutants (2) . This paper
coordinates the efforts from two EPA contracts in order to
use that methodology specifically for an evaluation of
formaldehyde.
Mathematical models were previously designed for various
scenarios for which mobile sources are the overwhelming
contributor to the exposure (such as garages, roadway
tunnels, expressways, and street canyons). These models were
used to calculate the ambient air concentrations resulting
from various mobile source formaldehyde emission factors
(mg/mile or mg/minute) (3) . These models were also used to
convert the ambient air range of concern to corresponding
vehicle emission ranges of concern for the various exposure
scenarios.
In conjunction with this, a formaldehyde health effects
literature search was conducted by Midwest Research Institute
under contract to EPA to aid in the determination of the
suggested range of concern (4). The literature review
focused on the toxicological (i.e., noncarcinogenic)
properties of formaldehyde rather than on its carcinogenicity
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to humans. The consideration of the potential
carcinogenicity of formaldehyde is important but beyond the
scope of this report. Some of the typical toxicological
health effects noted were eye, nose, throat and respiratory
tract irritation of various degrees, depending on exposure.
The results of the Midwest analysis suggest a range of
concern for ambient formaldehyde concentrations of
0.03 mg/m to 1.0 mg/m (0.02 ppm to 0.8 ppm) . .Using the
mathematical models developed for the roadway scenarios, this
range of concern corresponds to motor vehicle emissions
ranging from 10.5-350.1 mg/mile for a severe roadway tunnel
situation to 714.3-23,809 mg/mile for a typical street canyon
situation. For garage scenarios, the formaldehyde range of
concern corresponds to motor vehicle emissions ranging from
0.4-15 mg/minute for a severe personal garage situation to
7.7-256 mg/minute for a typical parking garage situation.
These ranges of vehicle emissions corresponding to the range
of concern are then compared to fleet average emissions to
determine if the fleet average emissions fall below, within
or above the range of concern for the various scenarios.
A summary of selected results can be found in Table S-I.
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Table S-I
Summary of Selected Results*
Severe Case
Fleet Conditions
CY 1978 Fleet
(includes 25%
malfunction)
25% of CY 1978
Fleet Composed
of Catalyst-
Equipped
Methanol-Fueled
Vehicles (25%
malfunction of
both current
fleet & methanol-
fueled vehicles)
100% of Fleet
Methanol-
Fueled,
25% Malfunction
Ambient Air
Scenario
(Severe Case)
Roadway Tunnel
Expressway
Street Canyon
Fleet Average
Emissions
(ing/mile)
25.41
36.64
27.24
Roadway Tunnel
Expressway
Street Canyon
Roadway Tunnel
Expressway
Street Canyon
27.11
36.44
31.55
32.21
35.83
44.50
Emissions (mg/fnile)
Corresponding to
Range of Concern
Relation of Fleet
Average Emissions to
Range of Concern
10.5 - 350.1
59.3 - 1976
106.4 - 3546
10.5 - 350.1
59.3 - 1976
106.4 - 3546
Within
Below
Below
Within
Below
Below
10.5 - 350.1
59.3 - 1976
106.4 - 3546
Within
Below
Below
*Garage scenarios are not included in this table due to the preliminary nature of the
test data. Refer to text of paper for discussion and results for the garage scenarios.
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The term "CY 1978" as used in this report and given in Table
S-I is defined as a calendar year (CY) 1978 fleet composed of
gasoline- and diesel-fueled vehicles. Fleet average
emissions for the CY 1978 fleet were calculated using vehicle
miles traveled (VMT) fractions representative of a 1978 fleet
together with available emission factor data for a variety of
different model year gasoline- and diesel-fueled vehicles.
Fleet average emissions for those conditions for which
methanol-fueled vehicles are introduced into the fleet were
also calculated using VMT fractions representative of a 1978
fleet and available emission factor data. Use of the 1978
VMT fractions results in the percentage of catalyst-equipped
light-duty vehicles being that present in 1978 rather than a
later year when more catalyst-equipped vehicles are on the
road.
Referring to Table S-I, based on the available data, the
estimated CY 1978 fleet emission factors are below the ranges
of concern for the street canyon and expressway scenarios,
and within the range of concern for the severe roadway tunnel
scenarios. Similar results are obtained if 25 percent of the
CY 1978 fleet is replaced with catalyst-equipped,
methanol-fueled vehicles meeting current HC, CO and NOx
emissions standards.
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The "severe case" methanol fleet situation was determined to
be that in which 100% of the fleet is methanol-fueled and
catalyst-equipped (75% properly functioning, 25%
malfunctioning) . Due to the limited data, the malfunction
chosen for the light-duty methanol-fueled vehicles was
removal of the catalyst. Since data were available for a
heavy-duty methanol-fueled engine operated with the partial
failure of a catalyst, this malfunction was chosen for the
heavy-duty engines. For the "severe case" methanol fleet
situation, the fleet emission factors are within the range of
concern for the roadway tunnel, but fall below the ranges of
concern for the street canyon and expressway scenarios.
Based on tests conducted with light-duty gasoline- and
diesel-fueled vehicles, parking and personal garage
exposures, under severe conditions, would fall within, but
not above the range of concern. With catalyst-equipped,
methanol-fueled vehicles, parking and personal garage
exposures would fall below the range of concern, based on the
limited number of tests that have been run. The fact that
idle formaldehyde emissions from the single methanol-fueled
vehicle tested were lower than those from the gasoline-fueled
vehicles tested suggests the small sample size may be
producing misleading results.
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It must be stressed that the range of concern for
formaldehyde suggested in this report is based on its
toxicological properties and not its potential
carcinogenicity. In addition, this report does not consider
the photochemical reactivity of formaldehyde; it is known
that formaldehyde has relatively high photochemical
reactivity. Consideration of the carcinogenicity and
atmospheric photochemical reactions of formald.ehyde and its
end products is important but beyond the scope of this report.
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I. Introduction
Aldehydes are a class of partially oxidized hydrocarbons
emitted from many sources, including mobile sources.
Formaldehyde, the most prevalent aldehyde in vehicle exhaust,
is currently unregulated from mobile sources. Formaldehyde
in vehicle exhaust is formed by the incomplete combustion
(partial oxidation) of the fuel.
Due to its toxic properties, characteristically pungent odor
and photochemical reactivity, tests have been conducted to
characterize formaldehyde emissions as a function of driving
cycle, fuel and emission control system. The results of
these emissions tests along with health effects data, as
summarized later in this report, are used to suggest the
conditions under which formaldehyde emissions could be of
concern with respect to public health and welfare.
In addition to examining formaldehyde emissions from diesel-
and gasoline-fueled vehicles, this report examines
formaldehyde emissions from methanol-fueled vehicles. This
was done because of the potential for increased use of
methanol as an automotive fuel. The Clean Air Act requires
EPA to evaluate the health risks of new vehicle technologies.
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In the interest of establishing a range of concern for levels
of formaldehyde in motor vehicle exhaust/ Midwest Research
Institute (MRI) compiled information on the noncarcinogenic
health effects of formaldehyde at different concentrations
(4) . The results of that work form the basis for the range
of concern suggested later in this report.
This report does not consider the photochemical reactivity of
formaldehyde; it is known that formaldehyde has relatively
high photochemical reactivity. Consideration of the
atmospheric photochemical reactions of formaldehyde and its
end products is beyond the scope of this particular report.
The methodology presented in this paper was developed for
analysis of an unregulated pollutant regarding only its
toxicological properties. It has not been applied to the
evaluation of any carcinogenic properties a pollutant might
possess. Therefore, this report also does not consider the
potential carcinogenicity of formaldehyde. Some animal tests
have indicated that formaldehyde may cause an increased
incidence of squamous cell (nasal) cancer in rats. The
federal government is currently developing a general policy
for use by federal agencies in regulating carcinogens. It is
expected that any needed regulations for mobile source
emissions of formaldehyde due to its potential
carcinogenicity would be handled under the general policy
being developed.
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II. General Information on Formaldehyde
Formaldehyde (HCHO) is a colorless gas with a
characteristically pungent odor. It is highly irritating to
the exposed membranes of the eyes, nose and upper respiratory
tract. Formaldehyde is the most common and important
aldehyde emitted into the air.
Several billion pounds of formaldehyde are produced
commercially each year in the United States (7) . Partially
because of formaldehyde's antiseptic properties, it is used
in the medical, brewing and agricultural industries. About
half the formaldehyde produced is used in the preparation of
urea-formaldehyde and phenol-formaldehyde resins. These
resins, in turn, are used in the production of plywood,
particleboard, foam insulation, and a wide variety of molded
or extruded plastic items.
Under certain conditions, formaldehyde can be released into
the environment over a prolonged period from resinous
products. These products include urea-formaldehyde foam
insulation, particle board and some plywoods. Additional
sources of formaldehyde include automotive exhaust, cigarette
smoke, incinerators and photochemical generation in the
ambient air.
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Formaldehyde is known to be a component of photochemical smog
formation. Photochemical smog is a form of air pollution
which arises from the reactions of oxides of nitrogen and
hydrocarbon compounds in the presence of sunlight.
Formaldehyde can be photooxidized with a nitrogen oxide
mixture in air to yield ozone, which is also toxic. Smog
often results in eye and throat irritation, odor, plant
damage and decreased visibility. Formaldehyde may account
for a large fraction of the eye irritation associated with
photochemical air pollution. As mentioned previously, the
formation or destruction of formaldehyde by photochemical
reactions is an important consideration but beyond the scope
of this report. This report will consider only that
formaldehyde directly emitted from vehicles.
In an automotive system, formaldehyde is formed by the
incomplete combustion (partial oxidation) of the fuel.
Formaldehyde emissions, in general, have been shown to
decrease when a catalyst is used for emission control.
Control of HC and CO emissions brings about a corresponding
reduction in formaldehyde emissions for most emission control
systems.
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III. Legislative Background
When the Clean Air Act was amended in August 1977, the
additions included sections 202 (a) (4) and 206(a) (3) which
deal with mobile source emissions of hazardous pollutants
from vehicles manufactured after 1978. These sections are
stated below:
202 (a)
"(4) (A) Effective with respect to vehicles and engines
manufactured after model year 1978, no emission control
device, system or element of design shall be used in a
new motor vehicle or new motor vehicle engine for
purposes of complying with standards prescribed under
this subsection if such device, system, or element of
design will cause or contribute to an unreasonable risk
to public health, welfare, or safety in its operation or
function.
(B) In determining whether an unreasonable risk exists
under subparagraph (A) , the Administrator shall consider,
among other factors, (i) whether and to what extent the
use of any device, system, or element of design causes,
increases, reduces, or eliminates emissions of any
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unregulated pollutants; (ii) available methods for
reducing or eliminating any risk to public health,
welfare/ or safety which may be associated with the use
of such devices, systems, or elements of design which may
be used to conform to standards prescribed under this
subsection without causing or contributing to such
unreasonable risk. The Administrator shall include in
the consideration required by this paragraph all relevant
information developed pursuant to section 214."
206 (a)
" (3) (A) A certificate of conformity may be issued under
this section only if the Administrator determines that
the manufacturer (or in the case of a vehicle or engine
for import, any person) has established to the
satisfaction of the Administrator that any emission
control device, system, or element of design installed
on, or incorporated in, such vehicle or engine conforms
to applicable requirements of section 202 (a) (4).
(B) The Administrator may conduct such tests and may
require the manufacturer (or any such person) to conduct
such tests and provide such information as is necessary
to carry out subparagraph (A) of this paragraph. Such
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requirements shall include a requirement for prompt
reporting of the emission of any unregulated pollutant
from a system device or element of design if such
pollutant was not emitted, or was emitted in
significantly lesser amounts, from the vehicle or engine
without the use of the system, device, or element of
design."
Prior to these amendments, EPA's guidance to the
manufacturers regarding hazardous unregulated pollutants were
contained in the Code of Federal Regulations, Title 40,
section 86.078-5b. This subsection is stated as follows:
"Any system installed on or incorporated in a new
motor vehicle (or new motor vehicle engine) to enable
such vehicle (or engine) to conform to standards
imposed by this subpart:
(i) Shall not in its operation or function cause
the emissions into the ambient air of any noxious
or toxic substance that would not be emitted in
the operation of such vehicle (or engine) without
such system, except as specifically permitted by
regulation; and
(ii) Shall not in its operation, function, or
malfunction result in any unsafe condition
endangering the motor vehicle, its occupants, or
persons, or property in close proximity to the
vehicle.
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(2) Every manufacturer of new motor vehicles (or
new motor vehicle engines) subject to any of
the standards imposed by this subpart shall,
prior to taking any of the action specified in
section 203 (a) (1) of the Act, test or cause to
be tested motor vehicles (or motor vehicle
engines) in accordance with good engineering
practice to ascertain that such test vehicles (or
test engines) will meet the requirements of this
section for the useful life of the vehicle (or
engine)."
Before certification can be granted for new motor
vehicles, manufacturers are required to submit a
statement, as well as data (if requested by the
Administrator), which will show that the technology for
which certification is requested complies with the
standards set forth in section 86.078-5(b). This
statement is made in section 86.078-23(d).
The EPA issued an Advisory Circular (AC) (5) in June 1978,
to aid the manufacturers in complying with section 202
(a) (4) . Manufacturers were asked to continue providing
statements showing that their technologies did comply with
the vehicle emission standards and also will not
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contribute to an unreasonable risk to public health.
Another Advisory Circular (6) was issued in November of
that year continuing these procedures for 1980 and later
model years. At that time/ EPA began work to develop and
implement a methodology which would provide a preliminary
assessment of potential mobile source unregulated
pollutant hazards in order to assist the manufacturers in
deciding which, if any, unregulated pollutants are of
particular concern.
Up to this time, several preliminary assessments have been
made covering sulfuric acid, hydrogen cyanide and
ammonia. In each of these cases, the preliminary
assessment found no reason for suspecting a public health
problem from the current fleet emissions of these
pollutants, and recommended that further monitoring may be
appropriate to be sure that new vehicle/emission control
system configurations did not result in greatly increased
emissions.
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IV. Methodology Overview
Along with the previously mentioned activities, EPA, with- the
input from several interested parties, has developed a
methodology which is one possible approach to implementing
section 202 (a)(4) of the CAA. This approach is explained in
detail in EPA report number EPA/AA/CTAB/PA/81-2, "An Approach
for Determining Levels of Concern for Unregulated Toxic
Compounds from Mobile Sources" (2) . Only a brief summary of
this method will be presented in this report.
Under contract to EPA, Southwest Research Institute (SwRI)
and Midwest Research Institute (MRI) have provided valuable
information for this effort. SwRI developed or modified
mathematical models for predicting ambient air concentrations
of mobile source pollutants for a variety of exposure
scenarios including enclosed spaces, street canyons, and
expressways. Once vehicle emission factors for various
vehicle categories have been determined for a particular
pollutant, these models can then be used to calculate
corresponding ambient air values for both severe and typical
exposure situations for each scenario.
Health effects literature searches have been conducted by MRI
in an attempt to aid EPA in suggesting a range of concern for
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various selected pollutants. with adequate information, the
limits for this range can be chosen. The upper level of the
range will be that pollutant concentration above which the
studies show that the pollutant causes so great a health
risk as to strongly suggest it be avoided. The lower value
of the range will be the lowest level at which there is
evidence of adverse physiological effects. The region
between these limits will be termed the "ambient air range of
concern", indicating scattered data points providing evidence
of adverse or physiological effects caused by exposure to
various concentrations of formaldehyde. Using the ambient
air vs. emission factor model developed earlier, the ambient
air range of concern can be expressed in terms of a vehicle
emission range of concern for each scenario. Any technology
emitting a pollutant falling within the range of concern
should be subject to closer scrutiny. Technologies with
emission levels which fall above the highest value of the
range should be considered "high risk" with respect to human
health.
For the purpose of this report, this particular methodology
has been used to develop a range of concern specifically for
motor vehicle emissions of formaldehvde.
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V. Vehicle Emissions of Formaldehyde
Formaldehyde exhaust emissions have been measured for a
variety of vehicle types. The EPA recommended procedure for
this measurement is described in an EPA report entitled,
"Analytical Procedures for Characterizing Unregulated
Pollutant Emissions from Motor Vehicles" (8). . The
recommended procedure/ commonly referred to as the 2,4
dinitrophenylhydrazone (DNPH) procedure, includes use of a
gas chromatograph (GC) and flame ionization detector (FID)
for analysis of formaldehyde and other individual aldehydes.
The DNPH procedure was used to obtain all the formaldehyde
data in this report. In some cases a high pressure liquid
chromatograph (HPLC) was used rather than a GC-FID for
analysis of formaldehyde. The use of two different
analytical techniques should not significantly affect the
results.
Formaldehyde emission factors for various vehicle types were
collected from several available sources and are listed in
Table I. Emission factor data were obtained for a variety of
different model year gasoline- and diesel-fueled vehicles.
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Table I
Gasoline- and Diesel-Fueled Vehicles-No Malfunction
Formaldehyde Emission Factors3
Formaldehyde (mq/mile)
Vehicle Category
Light-Duty Diesel Vehicles
Light-Duty Diesel Trucks'3
Light-Duty Gasoline Vehicles
Non-Catalyst; no air pump
Non-Catalyst; air pump
Oxidation Catalyst;no air pump
Oxidation Catalyst;air pump
3-way Catalyst; no air pump
3-way Plus Ox. Cat.; air pump
Light-Duty Gasoline Trucksc
Non-Catalyst; air pump
Catalyst; no air pump
FTP
21.21
21.21
48.79
15.62
2.28
4.65
0.35
2.57
15.62
2.28
Hot FTP
15.24
15.24
47.83
11.39
1.51
4.25
0.11
2.91
11.39
1.51
34.97
17.47
1.36
1.37
0.11
3.04
17.47
1.36
Heavy-Duty Diesel Trucks^
Heavy-Duty Gasoline Trucks^
Transient FTP Hot Trans. FTP
36.75
62.486
35.31
45.566
7 Mode
Steady State
123.85
174.38
a References 9, 10, 11, 12, 13, 14, 15, 16.
b Due to a lack of sufficient data, these values are assumed to be the same
as those given for light-duty Diesel vehicles.
c These values are assumed to be the same as those given for light-duty
gasoline vehicles.
d Heavy-duty engine data expressed as gAW-hr converted to mg/mile using
road fuel consumption test data from other heavy-duty engines.
e Due to a lack of sufficient data, these values are assumed to be the same
as those given for non catalyst, light-duty gasoline vehicles, with an
air pump, adjusted by a factor of 4 for approximate differences in fuel
consumption.
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Emission factors for low mileage light-duty vehicles were
compiled for the Federal Test Procedure (FTP), hot start FTP,
and Highway Fuel Economy Test (HFET) driving schedules.
Emission factors for the heavy-duty vehicles were compiled
for the transient FTP, hot FTP and 7 mode steady state
driving schedules.
The available data for the light-duty gasoline-fueled
vehicles list emission levels from both unmodified (i. e.,
properly tuned) and malfunctioning vehicles. The malfunction
modes evaluated for the non-catalyst and catalyst-equipped
vehicles were 12% misfire and disconnected EGR and/or 0-
sensor, respectively. These malfunction modes resulted in
the greatest increase in formaldehyde emissions. Average
malfunction emissions for each light-duty gasoline vehicle
category are given in Table II. These malfunction emissions
will be used when calculating fleet average emission factors
as discussed later in this report.
The emissions found for the malfunction modes are especially
important to this effort due to the fact that formaldehyde
emissions tend to increase under malfunction conditions.
iMaximum emission rates have been listed below for three
vehicle categories.
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Table II
Average Malfunction Emissions
Light-Duty Gasoline Vehicles*
Formaldehyde (mg/mile)
Hot Start
Vehicle Category FTP FTP HFET
Non-cat.; no air pump 208.80 237.49 199.34
Non-cat.; air pump 121.06 101.95 242.22
Ox. cat.; no air pump 7.03 4.04 4.38
Ox. cat.; air pump 8.08 7.77 9.01
3-way cat.; no air pump 1.58 1.30 0.56
3-way plus ox. cat.; air pump 1.42 1.43 0.48
*References 12, 13, 14, 15.
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Maximum Reported Formaldehyde Emission Rates a»b
(Highest Values Reported From Any Source On Any Single Test)
Light-Duty Gasoline Mg/Mile
Vehicle Category FTP Hot FTP HFET
Non-catalyst 340.38 369.30 338.29
Oxidation Catalyst 27.37 23.99 54.40
3-Way Catalyst 39.80 19.50 6.87
a References 12, 18, 19.
b Formaldehyde emissions from in-use vehicles and/or
vehicles operating under malfunction modes.
Data from in-use vehicles operating with or without
malfunctions were also examined and, where appropriate,
included in the above table. The maximum reported emissions
for the non-catalyst-equipped vehicles are higher than those
of the other two categories, and they are also much higher
than any of the vehicle categories listed in Table I.
Table III lists the formaldehyde emissions found for light-
and heavy-duty methanol-fueled vehicles. The heavy-duty
numbers are based on tests of only one engine (M.A.N. 100%
methanol/spark ignition engine). Formaldehyde emissions from
this heavy-duty engine were lower than those from the
light-duty vehicles when the transient FTP engine dynamometer
cycle was used. This appears to be an anomaly; the
heavy-duty emission factors given in Table III should be
updated as additional tests are run. The
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Table III
Methanol-Fueled Vehicles
Formaldehyde Emission Factors a
Formaldehyde (mg/mile)
Vehicle Category FTP Hot FTP HFET
Light-Duty Methanol Vehicles
Unmodified (no malfunction)
Oxidation or 3-Way Catalysts 21.67 6.79 2.20
Malfunction
Non-catalyst (catalyst- 123.55 116.98 83.25
equipped vehicles tested
without catalysts)
Transient Hot Trans. 7 Mode
FTP FTP Steady State
Heavy-Duty Methanol Engines D
Unmodified (no malfunction)
Oxidation Catalyst 3.09 0.00 158.78
Malfunction
Partial Failure of 9.27= 0.00 476.27
Oxidation Catalyst
^References 20,21,22,23.
bHeavy-duty engine data expressed as mg/kW-hr converted to
mg/mile using road fuel consumption test data from other
heavy-duty engines.
cSince data on the transient cycle are not available for this
malfunction, this emission factor was obtained by applying the
three fold increase found for the 7 mode data to the data on
the transient cycle obtained with the oxidation catalyst (3.09
x 3 = 9.27 mg/mile).
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formaldehyde emission factors given in Table III come from
vehicles or engines using 100% methanol fuel; formaldehyde
emissions from vehicles or engines using a gasoline-methanol
or diesel fuel-methanol mixture are not considered in this
paper. It should be noted that the formaldehyde emission
factors for the light-duty methanol-fueled vehicles are based
on tests of only a few vehicles. Formaldehyde emissions from
these vehicles appear to be well controlled. Additional
light-duty methanol-fueled vehicles should be tested to
confirm these findings.
It is assumed that current HC, CO, and NOx emission standards
will apply to future light-duty methanol-fueled vehicles, and
that these vehicles will require catalysts to meet these
emission standards. The hydrocarbon (HC) standard (e.g.,
0.41 g/mile for light-duty vehicles on the FTP) would
presumably apply only to the HC portion of any unburned
alcohol in the exhaust or evaporative emissions. Since HC
comprises only 50% of the mass of methanol, the standard to
be met for actual methanol emissions would in effect be
double that for gasoline (e.g., 0.82 g/mile for light-duty
vehicles on the FTP) . . Only light-duty methanol-fueled
vehicles which were equipped with catalysts and which met the
existing federal emission standards were used to generate the
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data in Table III. Conclusions in this report are therefore
not applicable to methanol-fueled vehicles which do not have
catalysts or methanol-fueled vehicles whose emissions without
malfunction would not meet current standards.
Data for the heavy-duty engine were given in terms of
mg/kW-hr. To put. these data in terms of mg/mile, they were
first converted to gAg fuel by dividing by the fuel
consumption (kg fuel/kW-hr). Then, using fuel economy data
from other heavy-duty diesel engines averaging roughly
56 liters/100 km (24), and adjusting for the different energy
content of methanol vs. diesel fuel, the corresponding
methanol emission factors were calculated. Like the
gasoline- and diesel-fueled vehicles, formaldehyde emissions
from methanol-fueled vehicles are shown to decrease
substantially when a catalyst is used for emission control.
A certain percentage of in-use vehicles typically operate in
a less-than-optimum condition, referred to in this report as
a malfunction condition. As discussed previously,
malfunction data are available for light-duty gasoline-fueled
vehicles. For methanol-fueled vehicles, however, data are
very limited. The malfunction data used for the light-duty
methanol-fueled vehicles were those data obtained when the
catalyst-equipped vehicles were tested without catalysts.
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Table III shows the dramatic increase in formaldehyde
emissions that results with this severe malfunction. The
"malfunctioning" (no catalyst) vehicle formaldehyde emissions
are roughly an order of magnitude greater than emissions from
non-malfunctioning catalyst-equipped vehicles. Limited data
are available for a methanol-fueled catalyst-equipped 1981
Ford Escort tested with the air injection and/or EGR
disconnected (23). Formaldehyde emissions with both the air
injection and EGR disconnected are comparable to the
formaldehyde emissions obtained when the vehicle was tested
without a catalyst.
Seven mode steady-state data exist for a heavy-duty
methanol-fueled engine operated with partial failure of the
oxidation catalyst. The data in Table III show formaldehyde
emissions to increase roughly three times with the partial
failure of the catalyst as compared to the functioning
catalyst. Since data on the transient cycle are not
available for this malfunction, the three fold increase found
for the 7 mode data was applied to the data on the transient
cycle obtained with the functioning catalyst. Unfortunately,
no data are available for the engine operated without the
oxidation catalyst.
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The potential effect of these malfunctions on ambient air
concentrations of formaldehyde is shown in columns 4 and 5 of
Table VII (in Section VI) with 25% of the vehicles assumed to
be malfunctioning.
The driving cycles considered in this report and given in
Tables I, II, and III were chosen to represent various
exposure scenarios. These scenarios and the driving cycles
chosen for each scenario will be discussed in the following
section (section VI) . In addition to the driving cycles
given in Tables I, II, and III, available formaldehyde idle
emissions data (mg/minute) were used to estimate formaldehyde
exposures in garage scenarios. This will also be discussed
in section VI.
Fleet Average Emissions
Using the formaldehyde emission factor data presented in
Tables I, II, and II, it is possible to calculate fleet
average emission factors. The additional information used to
make these calculations is listed in Table IV. A fraction of
the vehicle miles traveled (VMT) is listed for each vehicle
class. These data were derived from information presented in
the Pedco Report of 1978 (25) , and the EPA report, "Mobile
Source Emission Factors: For Low Altitude Areas Only" (26).
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30
Table IV gives the VMT mix for the 1978 fleet. This mix
tends to change from year to year with the introduction of
new engines and emission control systems, so the fleet
average emissions can be updated by modifying the'fleet VMT
mix data used in the calculations.
An example of this would be the quantity of non-catalyst
gasoline VMT relative to the VMT of catalyst-equipped
vehicles. Based on Table IV which reflects the makeup of a
1978 fleet, 57% of the total VMT (for light-duty and
heavy-duty vehicles) would be from catalyst-equipped vehicles
(with or without an air pump) and 24.5% would be from
non-catalyst-equipped light-duty vehicles. In later years,
the non-catalyst fraction of the total VMT is expected to
decrease. As a result, the formaldehyde fleet average
emission factors for later years (if based on a total VMT
composed of diesel and gasoline-fueled vehicles) are also
expected to decrease.
Each vehicle class VMT fraction is multiplied by the
corresponding emission factor (EF) for that class, giving a
fraction quantity of pollutant emitted from a particular
vehicle category in comparison to other vehicle categories in
the fleet. The EFxVMT fractions for each vehicle class are
calculated and then summed to obtain a total fleet average.
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31
Table IV
Fraction VMT For 1978 Fleet*
Vehicle Category
Light-Duty Diesel Vehicles
Light-Duty Diesel Trucks
Light-Duty Gasoline Vehicles
Non-Catalyst; no air pump
Non-Catalyst; air pump
Ox Cat.; no air pump
Ox Cat.; air pump
3-Way Cat.; no air pump
3-Way plus Ox. Cat.; air pump
Light-Duty Gasoline Trucks
Non-Catalyst
Catalyst
Heavy-Duty Diesel Trucks
Heavy-Duty Gasoline Trucks
Fraction
VMT
0.015
0.002
0.147
0.098
0.289
0.261
0.012
0.008
0.096
0.010
0.027
0.035
*References 25 and 26.
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32
The total fleet average then is based on VMT fractions for
the 1978 fleet together with emission factor data for a
number of different model year vehicles. For formaldehyde
emissions from the calendar year (CY) 1978 fleet (composed of
gasoline- and diesel-fueled vehicles), the fleet average
ranges from 13.63 mg/mile to 18.98 mg/mile, depending on the
driving cycle chosen. This takes into account only those
vehicle classes listed in Table IV. Of course, as mentioned
previously, should any of these categories change, so would
the total fleet average.
It is difficult to predict exactly what percentage of vehicle
categories will make up the entire fleet at any one time. In
order to account for differing proportions of malfunctions
and technologies, Table V was devised. Table V presents
fleet averages for the CY 1978 fleet and the CY 1978 fleet
with 25% of the light-duty vehicles malfunctioning. The
latter fleet average is based on the assumption that 25% of
the vehicle fleet operates in some, malfunction mode (i.e.,
misfire, disconnected 0. sensor, etc.) at any given time
(17)*. Further work may identify a more accurate percentage.
*Previous reports (38,39) on specific compounds evaluated for
Section 202(a)(4) of the Clean Air Act also used 25%
malfunction. This percentage is confirmed as a realistic
upper bound based on the 1982 EPA Office of Mobile Sources
Field Operations Support Division tampering survey results.
These results indicate that, for vehicles at the 50,000 mile
point in non-I/M areas, the tampering rate is approximately
26% when catalyst removal, disconnected air pump, and
habitual misfueling are considered.
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33
Table V
Total Fleet Averages
Formaldehyde (mq/mile)
CY 1978 Fleet
(no malfunction)
CY 1978 Fleet
(25% malfunction)
25% of CY 1978 Fleet <3
Composed of Catalyst-
Equipped Methanol-
Fueled Vehicles
(no malfunction)
25% of CY 1978 Fleet d
Composed of
Methanol-Fueled
Vehicles (both fleet
and methanol-fueled
vehicles contain 25%
malfunction)
100% of Fleet d
Methanol-Fueled
Vehicles
(25% malfunction)
FTP a
15.66
27.24
16.87
31.55
44.50
Hot FTP ° HFET c
13.63
25.41
11.82
27.11
32.21
18.98
36.64
17.21
36.44
35.83
alncludes LD FTP and HD Transient FTP emission factors.
blncludes LD Hot FTP and HD Hot Transient FTP emission
factors.
clncludes LD HFET and HD 7 Mode Steady State emission
factors.
dBased on a VMT mix of 93.8% LD/6.2% HD.
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34
Table V also presents fleet averages for hypothetical
situations in which 25% and 100% of the CY 1978 vehicle fleet
is replaced with light- and heavy-duty methanol-fueled
vehicles. For the two situations in which 25% of the CY 1978
fleet is replaced with methanol-fueled vehicles, 25% of the
CY 1978 light-duty fleet was replaced with light-duty
methanol-fueled vehicles and 25% of the CY 1978 heavy-duty
fleet was replaced with heavy-duty methanol-fueled vehicles.
The introduction of light-duty methanol-fueled vehicles into
the CY 1978 fleet is expected to have more effect on
formaldehyde emissions than the corresponding introduction of
heavy-duty methanol-fueled vehicles because light-duty
vehicles are estimated to comprise 93.8%-of the fleet.
From examining Table V, it can be seen that substituting 25%
of the CY 1978 fleet with light and heavy-duty
catalyst-equipped, methanol-fueled vehicles has little impact
on resulting fleet average formaldehyde emissions. This
occurs in spite of the fact that light-duty
catalyst-equipped, methanol-fueled vehicles emit greater
quantities of formaldehyde than their gasoline-fueled
counterparts. The reason is, by substituting 25% of the CY
1978 fleet with catalyst-equipped, methanol-fueled vehicles,
a portion of the non-catalyst-equipped, gasoline-fueled
vehicles are in the end result displaced. Non-catalyst-
equipped, gasoline-fueled vehicles emit greater quantities of
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35
formaldehyde than catalyst-equipped, methanol-fueled
vehicles. In reality, however, methanol-fueled vehicles
would be replacing primarily catalyst-equipped vehicles
rather than non-catalyst-equipped vehicles. In addition, the
number of non-catalyst-equipped vehicles will continue to
decrease in the future. These are weaknesses of the
simplistic partial replacement of the fleet with methanol-
fueled vehicles. Because of these weaknesses, this
replacement scenario does not provide an adequate one-to-one
comparison with continued current fleet sales.
The compiled fleet averages given in Table V will be used in
comparing vehicle emissions to the suggested range (s) of
concern. In subsequent steps, these fleet averages will be
used to calculate ambient concentrations of formaldehyde for
each situation.
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36
VI. Formaldehyde Ambient Air Concentrations
The formaldehyde emission factor information provided in
Tables I through V can be used in conjunction with the
modeling techniques developed by Southwest Research Institute
(SwRI) (3) , in order to calculate the ambient air
concentrations produced by varying levels of formaldehyde
vehicle emissions for different microscale exposure
situations. Future work may identify other scenarios which
would also be appropriate for the assessment of human
exposure to exhaust pollutants, but, for this task, only five
exposure scenarios were investigated: personal garages,
parking garages, roadway tunnels, street canyons, and urban
expressways. Actual locations and receptors representing
typical and severe exposure levels were chosen for each of
these scenarios. The mathematical models for each different
situation were chosen from the literature. No attempt was
made to develop new models, although existing models
sometimes required modification or use in a new manner to
most accurately define the ambient air concentrations. For
localized area sources, the literature search for models
produced several models that predicted concentrations
downwind of area sources, but none that predicted
concentrations within the area source itself; therefore, this
exposure situation, while possibly important, will not be
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37
considered. Each situation has been considered separately,
and, therefore, no cumulative effects have been determined at
this point. Reference (3) discusses in detail the reasoning
behind using these specified scenarios as well as the
information used in the determination of the modeling
techniques. It should be noted that another approach would
be to use an air quality model for a region as a whole;
however, EPA has not used this approach for unregulated
emissions, preferring localized situations since they are of
greatest concern.
Fleet averages for CY 1978 fleet and various methanol
situations, listed in Table VI, were used to estimate the
corresponding formaldehyde ambient air concentrations given
in Table VII. Table VII presents ambient air concentrations
of formaldehyde, as a function of vehicle emissions, for
seven ambient situations.
Garage scenarios are not included in the table, but are
described in the text because idle emissions are expressed in
terms of mg/minute rather than mg/mile, and are available for
only a limited number of vehicles.
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Table VI
Total Fleet Averages for Various Exposure Situations3
Formaldehyde (mg/mile)
Roadway tunnelp
Typical Severe
CY 1978 Fleet
(no malfunction)
CY 1978 Fleet
(25% malfunction)
25% of CY 1978
Fleet Composed of
Catalyst-Equipped
Methanol-Fueled
Vehicles (no
malfunction)
25% of CY 1978
Fleet Composed of
Methanol-Fueled
Vehicles (both
fleet and methanol-
fueled vehicles
contain 25%
malfunction)
100% of Fleet
Methanol-Fueled
Vehicles (25%
malfunction)
18.98
36.64
17.21
36.44
35.83
13.63
25.41
11.82
27.11
32.21
Street
Canyonc
15.66
27.24
16.87
31.55
44.50
Expressway^
18.98
36.64
17.21
36.44
35.83
aTotal fleet averages taken from Table V.
bTotal fleet average for the HFET cycle was chosen to
represent the typical case tunnel situation. Total fleet
average for the hot start portion of the FTP was chosen to
represent the severe case tunnel situation.
cTotal fleet average for the FTP cycle was chosen to
represent both the typical and severe case street canyon
situations.
ATotal fleet average for the HFET cycle was chosen to
represent the typical, severe and close proximity expressway
situations.
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Table VII
Anbient Air Scenarios *
Formaldehyde Concentrations (mq/m
Roadway Tunnel
Typical
Severe
Expressway
Typical
Severe
Close
Proximity
Street Canyon
Typical
Severe
CY 1978 Fleet
(no
malfunction)
0.021
0.039
0.002
0.010
0.002
0.001
0.004
CY 1978
Fleet
(25%
25% of CY 1978
Fleet Composed 25% of CY 1978
of Catalyst- Fleet Composed
Equipped of Methanol-
Methanol-Fueled Fueled Vehicles
Vehicles (no (25%
malfunction) malfunction) malfunction)
0.041
0.073
0.005
0.019
0.004
0.001
0.008
0.019
0.034
0.002
0.009
0.002
0.001
0.005
0.041
0.077
0.005
0.018
0.004
0.001
0.009
100% of
Fleet
Methanol-
Fueled (25%
malfunction)
0.040
0.092
0.004
0.018
0.004
0.002
0.013
*Garage scenarios are not included in this table due to the preliminary nature of the test
data. Refer to text of paper for discussion and results for the garage scenarios.
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Each scenario is intended to represent a specific type of
situation. The typical personal garage situation represents
a 30 second vehicle warm-up time and the severe situation
simulates a five minute vehicle warm-up time. Both of these
cases, of course, take place within a residential garage with
the door open, and are intended to correspond to summer and
winter conditions, respectively.
The typical parking garage case simulates an above the
ground, naturally ventilated garage in which it is assumed
that a vehicle spends an equal amount of time on both the
parking level and ramp level. The severe case represents an
underground garage wherein the exposed population is assumed
to be at parking level five (lowest level) . It is also
assumed that this exposure occurs 20 minutes after a major
event in which the parking structure is emptying from an
essentially full condition. The initial concentration of
formaldehyde is assumed to be low (0.001 mg/m ) .
In order to more closely assess public exposure to
formaldehyde in garage situations, idle and very low speed
emissions data were collected from six production vehicles
(27) . The vehicles included a 1970 non-catalyst-equipped
vehicle, 1978 and 1980 oxidation catalyst-equipped vehicles,
1981 and 1982 three-way, catalyst-equipped vehicles, and a
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1981 diesel vehicle. Idle data were collected to simulate
the personal garage situations. A modified version of the
New York City Cycle (NYCC) was developed to simulate low
speed operation that may be encountered in a typical parking
garage. The modified NYCC is 12 minutes in duration, has a
maximum speed of 21 miles per hour, an average speed of 2.5
miles per hour, and contains 68 percent idle' operation. With
the exception of the diesel vehicle, the vehicles were tested
unmodified and under malfunction operation. Formaldehyde
emissions at idle ranged from 0.00 to 3.43 mg/minute for the
unmodified vehicles, and from 0.00 to 3.97 mg/minute for the
malfunctioning vehicles. Formaldehyde emissions at low speed
ranged from 0.00 to 2.86 mg/minute for the unmodified
vehicles and from 0.12 to 1.97 . mg/minute for the
malfunctioning vehicles. Assuming worst case conditions
(idle: 0.00-3.97 mg/minute, low speed: 0.12-2.86 mg/minute),
formaldehyde ambient air concentrations for each of the
garage situations would be as listed below:
Diesel and Gasoline-Fueled Vehicles
Formaldehyde Ambient Air Concentrations (mg/m3)
Personal Garage Parking Garage
Typical Severe Typical Severe
0.000-0.031 0.000-0.266 0.000-0.011 0.007-0.159
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Currently, idle emission data for methanol-fueled vehicles
are available from one vehicle/ a VW Rabbit with a 3-way
catalyst (22) . Average formaldehyde emissions at idle are
0.26 mg/minute with the catalyst and 17.49 mg/minute without
the catalyst. Resulting formaldehyde ambient air
concentrations fo.r the methanol-fueled vehicle for each of
the garage situations would be as listed below:
Methanol-Fueled VW Rabbit
Formaldehyde Ambient Air Concentrations (mg/m3)
Personal Garage Parking Garage
Typical 'Severe Typical Severe
With Catalyst 0.002 0.017 0.001 0.014
Without Catalyst 0.138 1.172 0.068 0.974
Two specific tunnel designs were chosen to estimate the two
roadway tunnel cases. A newly designed, two lane roadway
tunnel, with moderate traffic flow, is used for the typical
condition, while an old design, heavily traveled roadway
tunnel is used for the severe condition. The HFET driving
cycle, with an average speed of 48.2 mph, was chosen to
represent the typical case tunnel scenario. For the severe
case tunnel scenario the average speed is 25 mph, so of the
data available, the hot start portion of the FTP was chosen
as representative.
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The street canyon situations are simulated by examining the
parameters of two street canyons. The most sensitive
parameter in this model appears to be the number of traffic
lanes within the canyon. The typical condition is calculated
for a two-lane street canyon with a traffic load of 800
vehicles per hour and a sidewalk location of the exposed
population. The severe condition is based on a six-lane
street canyon with a 2400 vehicles per hour traffic load, and
the exposed population is located inside the vehicles. The
FTP was chosen to represent the typical and severe street
canyon. The FTP, with an average speed of 19.6 mph,
simulates urban driving conditions including cold and hot
starts and stop and go driving.
Three different cases were considered in order to cover the
possible range of exposures in an expressway situation. The
typical, on road exposure is based on a four-lane expressway
with a traffic load of 1400 vehicles per hour and a westerly
wind (perpendicular to roadway) of 1.0 meter per second
(representing the most severe wind condition). In this
situation, the exposed population is located inside the
vehicle. The severe case represents a heavily traveled (3600
vehicles/hour), ten-lane freeway with a 1.0 meter/second
westerly wind (perpendicular to roadway), and an in-vehicle
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location of the exposed population. The third case is the
off-road case which estimates an exposure involving a close
proximity to the highway (i.e., living or working close to a
heavily traveled freeway). This case is calculated on a
short term basis (rush hour) for a distance of 100 meters
downwind of the roadway. The HFET was chosen to represent
the expressway scenarios.
From examining Table VII, resulting ambient air
concentrations of formaldehyde for the roadway scenarios
range from 0.001 to 0.092 mg/m depending on the scenario
and fleet situation chosen. Of the scenarios examined, the
severe roadway tunnel results in the "highest formaldehyde
concentrations. Similarly, of the fleet situations examined,
the 100% methanol fleet situation (with 25% malfunction)
results in the highest formaldehyde concentrations.
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VII. Formaldehyde Health Effects
A literature review concerning the health effects of
formaldehyde was performed as an input to the determination
of a suggested range of concern for mobile source emissions
of this compound (4) . The literature review and this report
focus on the noncarcinogenic effects of formaldehyde rather
than on its carcinogenicity to humans. The latter is an
unresolved question of much importance that will be discussed
briefly but is beyond the scope of this report.
Interpretation of the health effects of formaldehyde must
consider not only the concentration/ but also the duration of
exposure. The literature review examined both acute and
chronic exposure studies of animals and humans. Results of
selected acute and chronic exposure studies will be briefly
discussed.
Numerous studies have shown that formaldehyde is irritating
to the eyes and upper respiratory tract of laboratory
animals. The minimal adverse effects seem to be local
irritation and subsequent tissue reactions, especially in the
pulmonary system. Such adverse effects generally appear at
levels at or above 1 mg/m (0.8 ppm) , whether the animals
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46
w.ere acutely or chronically exposed. In chronic studies,
biochemical and inflammatory changes have been reported in
rats exposed for only 8-12 weeks to formaldehyde levels as
low as 0.012 mg/m (0.01 ppm) (4).
Formaldehyde is strongly irritating to the human eye, nose,
and throat and capable of causing allergic sensitization.
Acute human experimental exposure to formaldehyde
concentrations of 1.25-17.3 mg/m (1.00 - 13.8 ppm) results
in moderate to severe irritation of the eye, nose, and throat
(4). Exposure times ranged from 1.5 minutes (with multiple
exposures) to 5 hours. Clear irritation occurs among
subjects exposed to formaldehyde concentrations at or above
1.0 mg/m (0.8 ppm). At exposures of approximately 1.0
mg/m for 10 minutes or 5 hours, eye and respiratory tract
irritation is slight, odor is perceived, and other effects
such as changes in breathing rhythm and alpha-rhythms occur
(29,30,31). Slight eye, nose, and throat discomfort occurs
at a formaldehyde concentration of 0.3 mg/m (0.24 ppm)
when exposed 5 hours (29) . The threshold for eye irritation
is 0.2-0.25 mg/m (0.16 - 0.20 ppm) based on a single
exposure of 300 seconds (32) . The reported odor thresholds
range from 0.4 mg/m (0.32 ppm) to roughly 0.05 mg/m
(0.04 ppm) for sensitive subjects (33). Mood changes have
been reported for subjects exposed to formaldehyde levels as
low as 0.0024 mg/m (0.0019 ppm) (34).
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Repeated exposure to formaldehyde can cause sensitization in
certain individuals (such as people with allergies,
asthmatics and others with hyper-reactive airways).
Sensitization is an allergic process caused by repeated
exposure to certain substances. When exposed to
formaldehyde, these sensitized persons may exhibit allergic
dermatitis or mild to severe asthmatic reactions. There are
indications that some of the sensitized individuals may
develop increasingly severe reactions from subsequent
exposure to formaldehyde. It is estimated that fewer than
20% but perhaps more than 10% of the general population may
be susceptible to formaldehyde and may respond to extremely
low levels of formaldehyde (7) .
In occupational and residential studies, formaldehyde levels
of 0.036 - 4.98 mg/m (0.029 - 3.98 ppm) have been
associated with health effects such as eye, nose and throat
irritation, nausea, vomiting, diarrhea, headaches,
irritability and skin rashes (35). Case studies in mobile
homes which used particle board in the construction predict
that 20 percent of the adult population would experience eye
irritation at a formaldehyde level of 0.25 mg/m (0.2 ppm)
(36) . In one group of mobile homes where consumers had
health complaints, 90 percent of the formaldehyde
concentrations measured were below 0.12 mg/m (0.10 ppm)
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48
(35).. Using data available to the Consumer Product Safety
Commission as of April 1981, the average level of
formaldehyde measured in homes with urea formaldehyde foam
insulation was 0.14 mg/m (0.12 ppm) and in homes without
urea formaldehyde foam insulation the level was 0.036 mg/m
(0.03 ppm) (35). Many (31.6 percent) of the complaint
residences with urea formaldehyde foam insulation in which
formaldehyde measurements were made had levels of
formaldehyde at or below 0.13 mg/m (35).
Nonsmoking and smoking humans have been found to contain
formaldehyde in the breath at levels as high as 0.1 mg/m
(0.08 ppm), formaldehyde being a normal metabolite and a
metabolite of exogenous substances (37) . The American
Industrial Hygiene Association (AIHA) recommends an outdoor
ambient air formaldehyde standard of 0.12 mg/m3 (0.1 ppm).
Preliminary results of a 24-month chronic-inhalation study
sponsored by the Chemical Industry Institute of Toxicology
(CUT) have shown that formaldehyde is a carcinogen in rats.
Groups of 120 male and 120 female rats were exposed by
inhalation to 0, 2, 6, or 15 ppm formaldehyde vapor 6 hr/day,
5 days/week for 24 months. After 18 months, 36 of 240 rats
exposed to a formaldehyde level of 15 ppm were found to have
squamous cell carcimomas in the nasal cavities. Similar
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tumors were not detected in rats exposed for 18 months to 2
or 6 ppm or in mice exposed to 2, 6, or 15 ppm formaldehyde.
The frequency of nasal cancers through the 18-month sacrifice
was reported by Swenberg et al. (28) . Later, the CUT
reported at the Formaldehyde Symposium on November 20-21,
1980, in Raleigh, N. C,, that nasal cancer had been observed
in two rats exposed at 6 ppm for 24 months and in two mice
exposed at 15 ppm for 24 months. By the end of 24 months, 95
rats exposed to 15 ppm had developed nasal cancers. Although
there is no direct evidence of the carcinogenicity of
formaldehyde in humans, these results provide evidence that
formaldehyde might represent a carcinogenic risk to humans.
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VIII. Determination of the Range of Concern and Conclusions
The definition of "range of concern" is that range of
exposure concentrations suspected (but not confirmed) to be
detrimental to human health. The lower value of this range
would be the lowest concentration at which there is some
suggestion of adverse physiological effects. The upper value
of this range would be that level above which the studies
show that the pollutant causes so great a health risk as to
strongly suggest it be avoided. Although it would be more
appropriate to indicate the exposure time relative to its
corresponding concentration which tends to cause adverse
health effects, exposure times vary considerably among the
available studies. The determination of the range of concern
was based primarily on acute human experimental studies since
these were thought to most closely simulate the exposure
situations examined in this report.
The range of concern for formaldehyde is based on an
examination of relevant studies pertaining to noncarcinogenic
health effects, primarily acute human experimental studies.
Because formaldehyde is a strong irritant of the eyes, nose,
and throat and is also capable of causing an allergic
sensitization among the exposed population, special emphasis
will be given to the levels of formaldehyde found to cause
discomfort, where ordinarily this type of effect may not be
considered an "adverse" health effect.
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The range of concern is suggested to be 0.03 mg/m - 1.0
mg/m3 (0.02 - 0.8 ppm) . The suggested upper level is 1.0
mg/m because of the wide evidence of clear irritant
effects among individuals acutely exposed at this level. The
suggested lower level is 0.03 because the numerous animal
data, ijE directly extrapolatable to humans, dictates a level
of 0.01-0.04 mg/m . In addition, a human odor threshold as
low as 0.05 mg/m has been reported for sensitive
populations. The capability of formaldehyde to affect
allergic sensitization cannot be overemphasized as an
additional rationale for caution. In relation to the
Threshold Limit Value* (TLV) of 3 mg/m for formaldehyde,
the lower level is l/100th the TLV. This lower limit is
somewhat conservative considering that formaldehyde levels in
homes without urea formaldehyde foam insulation average 0.036
mg/m and that formaldehyde in human breath is as high as
0.1 mg/m .
Between the chosen limits of the range (0.03-1.0 mg/m ),
there are scattered data points providing evidence of adverse
physiological effects caused by exposure to various
concentrations of formaldehyde.
*The Threshold Limit Value, set by the American Council of
Governmental Industrial Hygienists, is the recommended
maximum time weighted average concentration to which workers
can be exposed for an 8-hour work day or 40-hour work week.
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The next step in making use of this range of concern is to
translate it into terms of automotive emission factors for
each public exposure scenario.. Table VIII lists the fleet
average emission factors which correspond to the upper (1.0
•5 O
mg/m ) and the lower (0.03 mg/m ) limits of the suggested
ambient air range of concern. Inspection of this table shows
that the scenarios.result in a wide range of emission factors
corresponding to the health effects range of concern of 0.03
mg/m to 1.0 mg/m . From this table the severe cases,
especially for the tunnel scenario, are the ones which
require further investigation. Using the fleet average
emission factors from Table VI the emission factors for each
scenario can be compared to the corresponding range of
concern. This comparison is given in Table IX. The fleet
average emission factors for the two "worst case" fleet
situations were selected for comparison. (To compare the
other fleet situations their fleet average emission factors
in Table VI can be compared to column A of Table IX). Garage
scenarios will be considered separately.
As shown in Table IX, even if it is assumed that the CY 1978
fleet is operating with 25% malfunction, the fleet average
emission factor could be within, but not above the range of
concern for the severe roadway tunnel situation.
Formaldehyde emissions for the street canyon and expressway
scenarios appear to be below the range of concern for the
current fleet situations explored in this report.
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Table VIII
Emission Factors Corresponding to the
Lower and Upper Limits of the Formaldehyde Range o£ Concern
Ambient Air Scenario
Em i s s i o n
Factor
(mg/mile)
corresponding
to a 0.03 mg/m3
exposure
Emission
Factor
(mg/mile)
corresponding
to a 1.0 mg/m3
exposure
Roadway Tunnel
Typical
Severe
Street Canyon
Typical
Severe
Expressway
Typical
Severe
Off Road
Parking Garage*
Typical
Severe
Personal Garage*
Typical
Severe
26.7
10.5
714.3
106.4
241.9
59.3
285.7
7.7
0.5
3.8
0.4
890.5
350.1
23,809
3546
8065
1976
9524
256
18
127
15
*Emission factors are given in mg/minute for garage exposures.
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Table IX
Range of Concern Compared to Potential Emissions
ABC
Fleet Average
Range of Concern Emissions(mg/mile;
(Severe Case) Fleet Average Assuming 100%
i.e., Fleet Average Emissions(mg/mile) Methanoi Fueled
Emissions (mg/mile) Assuming CY 1978 Catalyst-Equipped
Needed To Be of Fleet with 25% Vehicles with
Concern3 Malfunction13 25% Malfunction13
Roadway Tunnel 10.5-350.1 25.41 32.21
Street Canyon 106.4-3546 27.24 44.50
Expressway 59.3-1976 36.64 35.83
aFrom Table VIII.
Table VI.
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The highest emission rate reported for formaldehyde is 369.30
mg/mile from a non-catalyst-equipped vehicle. This is above
the range of concern for the severe roadway tunnel, but
within the range of concern for the severe street canyon and
expressway scenarios. Highest formaldehyde emission rates
for oxidation catalyst-equipped vehicles (54.40 mg/mile) and
3-way catalyst-equipped vehicles (39.80 mg/mile) fall within
the range of concern for the severe roadway tunnel scenario
but fall below the range of concern for the severe street
canyon and expressway scenarios. These emission rates are
for unique vehicles, and it is extremely unlikely that the
average emission rate of vehicles in a tunnel would ever be
so high.
Referring again to Table IX, for the "worst case" methanol
fleet situation given, the fleet average emission factors are
within, but not above the range of concern for the severe
roadway tunnel situation. As with the CY 1978 fleet
situation, the street canyon and^expressway scenarios do not
appear to present any possible problem regarding formaldehyde
exposure for the methanol situations explored in this report.
Garage scenarios were discussed in Section VI. Based on low
speed and idle tests conducted with light-duty gasoline- and
diesel-fueled vehicles, parking and personal garage
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exposures, under severe conditions would fall within, but not
above the range of concern. Parking and personal garage
exposures with methanol-fueled, catalyst-equipped vehicles
would on average fall below the range of concern, based on
the limited number of tests that have been run. Emissions
from a malfunctioning, methanol-fueled vehicle (i.e., one in
which the catalyst was removed) could fall above the range of
concern for the severe personal garage situation; however, it
is extremely unlikely that emissions from a methanol-fueled
vehicle in a garage would ever be so high.
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